1. Field of the Invention
The present invention relates to a polarizing plate used for a liquid crystal display (LCD) and a liquid crystal display using such a polarizing plate.
2. Description of the Prior Art
Recently, the demand for LCDs used for devices, such as personal computers has increased sharply. Applications for LCDs have also broadened. Recently, LCDs are used for monitoring as well.
A polarizing plate used for a LCD may be manufactured, for example, by a method including the steps of: dyeing a polyvinyl alcohol (PVA) film with dichroic iodine or a dichroic dyestuff; crosslinking the film with boric acid, borax, or the like; stretching the film uniaxially, followed by drying the film and sticking it to a protective layer such as a triacetylcellulose (TAC) film. The respective steps of dyeing, crosslinking and stretching are not necessarily carried out separately and can be carried out simultaneously. Furthermore, there is no limitation on the order of the steps.
When a polarizer is used after being formed, it may deteriorate due to problems in handling or the influence of moisture. Therefore, protective layers, such as triacetylcellulose films etc., are attached to both surfaces of the polarizer, thereby producing a polarizing plate.
In the above-mentioned configuration, when the polarizing plate is cut out into a size on a liquid crystal panel, both surfaces of the polarizer are covered with the protective layers such as triacetylcellulose films etc. but the polarizer made of a hydrophilic high polymer film is exposed at the sides of the cut-out polarizing plate. As a result, in conventional polarizing plates used for liquid crystal displays have a problem in that the change in dimension may be increased due to the change of moisture in the polarizer when left at high humidity for a long time. This may lead to problems in handling a panel when a liquid crystal panel is equipped, or to deterioration of the polarizing function.
In one aspect, the present invention relates to a polarizing plate having humidity durability, and a liquid crystal display using such a polarizing plate.
In one embodiment of the present invention, the polarizing plate includes a polarizer having all surfaces and sides covered with low moisture-permeable layers having moisture permeability of 310 g/m2xc2x724 h or less.
In some embodiments, the polarizing plate has a rate of change in dimension in the uniaxially stretching direction of xc2x10.1% or less after left at a temperature of 60xc2x0 C. and humidity of 95% for 100 hours.
In some embodiments, the polarizing plate is formed into a size of 90 mmxc3x9790 mm and attached to a plastic cell having a size of 100 mmxc3x97100 mm and a thickness of 400 xcexcm and made of a thermoplastic resin or a thermosetting resin, such that when the cell is left at a temperature of 60xc2x0 C. and humidity of 95% for 100 hours, the amount of warping at four corners of the cell is xc2x13.0 mm or less. In some embodiments, the thermoplastic resin is at least one selected from the group consisting of polycarbonate, polyalylate, polyether sulfone, polysulfone, polyester, polymethyl methacrylate, polyetherimide. In some embodiments, polyamide; and the thermosetting resin is at least one selected from the group consisting of epoxy resin, unsaturated polyester, polydiaryl phthalate and polyisobonyl methacrylate.
In some embodiments, the polarizing plate includes a reflector or a transreflector attached to the polarizing plate.
In some embodiments, the polarizing plate includes a retardation plate or a xcex plate attached to the polarizing plate.
In some embodiments, the polarizing plate includes a viewing angle compensating film attached to the polarizing plate.
In some embodiments, the polarizing plate includes a brightness-enhanced film attached to the polarizing plate.
In some embodiments of the invention, a liquid crystal display uses a polarizing plate in accordance with the invention on at least one side of a liquid crystal cell.